Field of the Invention
The invention relates to motor vehicle controllers and, more particularly, to a control unit for an automatic transmission of a motor vehicle. The controller or control unit defines an actuation signal for the transmission as a function of a variable which defines the output torque desired by the driver, of a measured variable which defines the engine speed or the vehicle speed, and, if appropriate, of further measured variables. The system has a classification system to which the measured variables, or parameters derived therefrom are fed as input variables and by means of which an output variable is generated with reference to an evaluation of the measured variables and parameters, with which output variable, in accordance with prescribed assignments, the driving behavior of the driver, the respective driving state or the respective load state of the motor vehicle is taken into account during the determination of the transmission ratio. If the transmission is a step-by-step variable speed transmission, then the controller generates actuation signals or shift signals with which the respective most favorable gear speed is selected. If the transmission is an infinitely variable speed transmission, the actuating signal controls the transmission ratio. Controllers of this type are also used, analogously, in the context of other devices or assemblies in motor vehicles, such as a traction controller or a rear wheel steering system.
Modern transmission controllers adapt the selection of the gear speed or transmission ratio to, inter alia, the driving behavior of the driver and/or the route In the first case, the behavior of the driver is evaluated by reference to characteristic input variables of the controller and derived variables calculated therefrom (referred to below as derivatives or else parameters), and it is converted into a modified transmission ratio selection adapted to the driver. See European application EP 0 638 742 and U.S. Pat. No. 4,679,145 (German patent DE 33 41 652 C2). The knowledge which is stored in the controller in the form of a reference and with which, for example, the driver is classified as "steady", "normal", or "sporty", is permanently prescribed here and there is always a fixed assignment between a behavior of the driver and a "driver class." Thus, frequent and rapid movement of the accelerator pedal, for example, will always lead to a sporty evaluation of the driver and to the activation of a corresponding transmission ratio selection, i.e. for example to shifting up at relatively high rotational speeds.
However, such a fixed assignment is not satisfactory in all cases. For example, it is perfectly possible for an objectively rather steady driver, i.e. a driver who does not require high driving performance and acceleration, nevertheless, for some reason, to make frequent and rapid pedal changes. This can lead to an incorrect adaptation of the control system. It is also possible that the gear-shifting behavior or transmission ratio selection assigned to the driver by the controller simply does not correspond to what she imagines as her ideal.
There are also other basic functions of an adaptive transmission controller which, owing to the generally fixed assignment, cause the controller to behave in a way which is not accepted by the driver. This is a result not only of the different personal wishes of drivers but also can be due to the fact that there are different driving habits in different countries. For example, an active gear-shifting strategy, which is heavily influenced by manually shifted transmissions, is generally considered ideal in Europe, while the typical driver in the United States prefers the traditional automatic transmission controller which uses manually selected gear-shifting patterns. A system which is highly adaptive in accordance with European habits will not generally be accepted in the United States.
An example of different drivers' wishes is the adapted gear-shifting behavior on an uphill route. From a technical point of view, the selection of a prescribed gear-shifting pattern which prevents so-called oscillating in the gear-shifting in a step-by-step variable speed transmission is most expedient. For this purpose, shifting-up operations are generally displaced to a higher traveling speed. However, this may be disruptive for those drivers who are accustomed to an absolutely fixed relationship between one position of the accelerator pedal, one speed of the vehicle and the respective transmission ratio or the respective gear speed, and thus prefer such a constant control behavior. In order to be able to satisfy such drivers with an adaptive transmission controller, it is therefore necessary to be able to correct or modify the "fixed knowledge" stored in the transmission controller.